Explosive bolt



March 26, 1968 v. J. MENICHELLI EXPLOS I VE BOLT Filed Dec. 17, 1965 PM I! Vincent J. MenicheHi INVENTOR.

BY ATTORNEY gal/M 4 AGENT.

United States Patent .Ofi ice ABSTRACT OF THE DISCLOSURE A mechanical fastening device severable by the detonation of a small quantity of explosive contained within the body of the device. The explosive is so located that separation occurs axially. There being no weakened or notched section, the device has a high tensile strength.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to a severable mechanical fastening device and in particular to a device which is severable by the detonation of a small quantity of explosive contained within the body of the device. I

Prior art devices generally employ a hollow body having an external or internal notch machined thereon to provide the device with a weakenedportion. This weakened portion provides an area of reduced cross-section which is severed upon detonation of the explosive charge contained within the device. The strength of these prior devices was limited to the crosssectional area of the hollow body at the weakened or notched section. Different methods of increasing the strength of these devices have been attempted, including the enlargement of the device but to date none have been effective.

The severable mechanical fastening device according to this invention which is more particularly set forth hereinafter, is shown and described in the general form of a nut and bolt. It will be understood, however, that the showing is for illustrative purposes only and not by way of limitation.

A severable mechanical fastening device according to this invention relates to a new and improved exploding bolt having a substantially increased structural strength while not requiring a larger explosive charge to sever the bolt. The bolt comprises a first portion and a second portion integrally formed therewith, the second portion being of greater diameter than the first portion and having an axial bore formed therein to receive an explosive charge. The explosive charge is axially spaced apart from the juncture of the first and second portions to prevent weakening of the bolt structure, but when the explosive charge is detonated shear forces are developed at the juncture of the first and second bolt sections to severe the bolt at said juncture.

It is therefore an object of this invention to provide a mechanical fastening device which is severable upon the detonation of an explosive charge contained therein.

Another object of this invention is to provide a mechanical fastening device which is severable within a predetermined area of the body of the device upon the detonation. of an explosive charge.

Still another object of this invention is the provision of an explosively severable mechanical fastening device which contains no weakened sections and is therefore able to withstand high stresses.

A further object of this invention is the provision of an explosively severable mechanical fastening device which is capable of reliably functioning on land, in the air or under water.

3,374,702 I I Patented Mar. 26, 1968 Other objects and many of the attendant advantages of this invention will be readily understood by reference to the following detailed accompanying drawings wherein:

FIG. 1 is a cross-sectional view of the explosive bolt contemplated by this invention; and I FIG. 2 is a cross-sectional view of of FIG. 1 after detonation.

A conventional exploding bolt would comprise a head attached to a hollow shank, which has a threaded outer end upon which a nut may be threaded, A hollow space within the shank contains an explosive charge and anelectrical detonator. When the detonator is actuated the bolt is sheared or blown apart at the weakened or notched portion. This weakened portion of the bolt limits the amount of longitudinal stress that may be applied'to the bolt thereby limiting the application of various size bolts. By using an explosive bolt having a weakened portion located thereon, an oversize bolt having the required strength characteristics must be used in situations which require the bolt to stand up to heavy load conditions.

The present invention, as shown in FIGS. 1 and 2 overcomes the above-mentioned handicap by eliminating the weakened portion without changing the amount of explosive charge that is needed to sever the bolt. In particular, FIG. 1 shows a bolt 27 holding a hatch 29 to the bulkhead 31 of a vessel. The bolt has an elongated first portion or shank 22 with threads 26 located on one end thereof. A nut 28 is threaded on the shank and acts against a plurality of washers 30 to hold the respective portions of the vessel together. A second larger diameter portion or head 24 is fixed to the shank so as to form a shoulder or juncture 36 therebetween. An explosive charge 34 having an electrical detonator 32 is located in a hollow space 23 within the head portion 24. The explosive charge and detonator are held within the head 24 by means of a cap 25 which is screw threadedly attached to the head portion. It is to be noted that the explosive charge 34 is spaced from the juncture of the shank and head portions so as to form a wall of metal between the end of the hollow space 23 and the shoulder 36.

As shown, the shoulder 36 has a curved wall but it is to be understood that this wall could be of any shape, e.g. flat or concave, depending on the specific application of the bolt. Furthermore, as shown the shoulder 36 ends in a groove 38, but, this groove is not required and merely serves as a guide when shearing forces are applied to the juncture.

Upon detonation of the explosive charge the interaction of the shock Waves thus produced are utilized to sever the bolt in an axial direction, as shown in FIG. 2. A bolt severed in this manner produces. a clean break as shown at 39 and 40, without any protrusion being formed on the shank portion 22 which might catch on one of the washers 30. This added feature of reliability greatly enhances the use of such an explosive bolt in hard to reach places such as under water at depths of up to 2000 feet or in any other situation where reliability, high strength and quick disassembling may be needed.

By eliminating the weakened portion upon which the explosive charge usually acts, a substantially improved explosive bolt capable of withstanding stresses up to three times as large as those which a conventional explosive bolt having the same dimensions can withstand has been produced. As noted previously, this added strength is achieved without raising the amount of explosive charge needed to sever the bolt. This is brought about by using the unique interaction of shock waves produced at the juncture of the shank and the head portion upon initiation of the explosive charge. Instead of being literally blown apart in a radial direction as in conventional bolts, the present invention severs the shank from the head in the axial direction therefore acting in the explosive bolt 61 sufficient thickness to prevent weakening of the shoulder order to provide a bolt which contains no weakened sections and is therefore able to withstand high stresses, the cross sectional area of the shank 22 is designed to be less than or equal to the cross sectional area of a frustrum of a cone described by rotation of a line 40 drawn from the bore or hollow space 23 to the intersection 3-8 of the first portion 22 and second portion 24 about the bolt axis.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An explosively severable mechanical fastening device comprising:

7 a first elongated cylindrical portion,

a second cylindrical portion of larger diameter than said first portion and formed integrally therewith to form a shoulder between said portions,

.said second cylindrical portion having defined therein an axial bore terminating short of said shoulder,

the cross sectional area of said first cylindrical portion being less than or equal to the cross sectional area of a frustrum of a cone described by rotating a line drawn from said bore to the intersection of said first and second cylindrical portions about the axis of said fastening device, and

an explosive charge received within said axial bore having an electrical detonator associated therewith whereby when said explosive charge is initiated shear forces are developed to sever said device at said shoulder.

2. The mechanical fastening device of claim 1, wherein said axial bore terminates a suflicient distance from said shoulder so as to provide a cross section at said shoulder port-ion when the fastening device'is under high stresses, whereby the shear forces developed by the detonation of the explosive charge act in an axial direction against the area of said first portion. 7 I

3. The mechanical fastening device of claim 1, in which a wall is formedbetween the end of the axial bore and saidshoulder' to prevent weakening of the device. 4. The mechanical fastening device of claim 1, wherein a cap is mounted on said second cylindrical portion to hold said detonator and explosive charge within said axial bore.

5. The mechanical fastening device of claim 4, in which the axial bore is formed entirely within said second cylindrical portion with a wall formed between an end of said bore and said shoulder whereby the shear forces developed by-the detonation of said explosive charge act in an axialdirection against'the area of said wall.

6. The mechanical fastening device of claim 5, wherein said-first cylindrical portion is uniform in cross-section along the length thereof.

7. The mechanical fastening device of claim 5, in which said wall portion and said first portion are severed from said second portion upon initiation of said explosive charge.

References Cited UNITED STATES PATENTS MARION PARSONS, JR., Primary Examiner. 

